Self-tightening keyless chuck

ABSTRACT

The present invention relates to a self-tightening keyless chuck to enable electric percussive drills to grip a tool shank. The chuck includes a rear sleeve, a body, a bearing ring, a bearing assembly, a nut, a jaw, a front sleeve and a stopper and so on. The bearing assembly utilizing a ball bearing is positioned with a circumferential arcuate race with a fixed depth, and the bottom surfaces of said circumferential arcuate race are provided with a plurality of ball-shape grooves. During the chuck grips a tool shank, the balls of said ball-bearing enter into the ball-shape grooves and are locked there, so as to prevent the tool from loosening due to the percussion vibration. In addition, the front sleeve engages with said nut through radial smooth press-fit to securely transmit a torque.

FIELD OF THE INVENTION

The present application relates to a keyless chuck and, moreparticularly, to a self-tightening keyless chuck. Generally, an electricpercussive drill is capable of reciprocating, percussive vibration aswell as rotary motion. Therefore, the present invention particularlyprovides a self-tightening keyless chuck for maintaining a secure gripon such a tool in percussive motion.

BACKGROUND ART

A variety of keyless chucks have been developed so far. A conventionalchuck generally comprises a rear sleeve, a body, a bearing ring, abearing, a nut, a jaw, a front sleeve, a stopper and so on. The jawextends/retracts under the rotation of the nut and the engagement ofconical threads, and the nut is rotated by movement of the front sleeve.Such a chuck is keyless if the front sleeve is rotated by hand. Thechuck may be attached to a driving shaft of a drill by means of threadsor a conical bore.

A conventional keyed or keyless chuck has the disadvantage that becausethe nut and the jaw are secured only by rotation of threads, the jawtends to loosen its grip on a tool due to axial percussive vibrationstransmitted through the chuck and the tool during operation. This willcause the tool to skid, thus resulting in a loss of working efficiencyand a loss of safety.

A conventional chuck is disclosed in Chinese Patent PublicationCN1040732C, in which the anti-percussion of the chuck is achieved byforming spokewise grooves in the surfaces of two members that act asbearing races, the opposing sides of the grooves being provided withround angles of different radii. The depth of the grooves has a greatinfluence on the anti-percussion ability of the chuck as well as on therelease of the chuck. If the grooves are too deep, the chuck will not bereleased after use. If the grooves are too shallow, the chuck will havea poor anti-percussion performance. Therefore, in order to keep auniform depth of the grooves in all members to thereby ensure theanti-percussion ability of all chucks, it is necessary to frequentlyadjust the machine for manufacturing the members. This, however, willaffect the efficiency of production and can result in an increase ofdefective products. To overcome this drawback, it is necessary toprovide a pressing machine with a higher pressing accuracy or largertonnage, which however will increase the cost of production.

Furthermore, the front sleeve of a conventional keyless chuck isgenerally made of plastic. The chuck generally has a configuration inwhich a steel ring is embedded in an inner side of the plastic frontsleeve, and two nut halves that are placed in a circular groove in thebody of the chuck are press-fit into the hole of the steel ring embeddedin the inner side of the plastic front sleeve, thereby securing the twonut halves in the circular groove in the body. This configuration,however, is complicated in structure and manufacturing process, and thefront sleeve of the chuck which has a low strength is susceptible todamage.

SUMMARY OF THE INVENTION

To overcome the aforementioned disadvantages and drawbacks in the priorart, the present invention provides a safe and simple self-tighteningkeyless chuck, which has a locking function and improves the strength ofa front sleeve and which is less susceptible to loosening when used fora percussive tool.

In order to fulfill the above object, the present invention employs thefollowing technical solution.

The invention provides a self-tightening keyless chuck for gripping atool shank, comprising a rear sleeve, a body, a bearing ring, a bearingassembly, a nut, a jaw, a front sleeve and a stopper, wherein thesurface of at least one of the bearing ring and the nut that faces thebearing assembly is provided with a recessed circumferential arcuaterace, and a plurality of ball-shape grooves are uniformly formed in anarcuate bottom surface of the arcuate race, and wherein the front sleeveengages with the nut through radial smooth press-fit.

The nut is provided with two angularly-cut split notches that aresymmetrically positioned on both ends of a diameter of the nut, theangularly-cut split notches having a cut-out angle between 30 and 75°.

Alternatively, the invention provides a self-tightening keyless chuckfor gripping a tool shank, comprising: a rear sleeve, a body, an upperbearing ring, a bearing assembly, a lower bearing ring, a nut, a jaw, afront sleeve and a stopper, wherein the surface of at least one of theupper and lower bearing rings that faces the bearing assembly isprovided with a recessed circumferential arcuate race, and a pluralityof ball-shape grooves are uniformly formed in the arcuate bottom surfaceof the arcuate race, and wherein the front sleeve engages with the nutthrough radial smooth press-fit.

In this self-tightening keyless chuck, the nut is provided with twoangularly-cut split notches that are symmetrically positioned on bothends of a diameter of the nut, the angularly-cut split notches having acut-out angle between 30 and 75°. Further, two parallel cut-out surfacesare symmetrically formed on the outer peripheral surface of the nut,which extend downwards in an axial direction from the front end surfaceof the nut by one third of the thickness of the nut and are located atan angle of 90° relative to the positions of angularly-cut splitnotches.

The front sleeve is press cast using a press-casting metal or a powderedmetallurgic material.

In the above two self-tightening keyless chucks, the recessedcircumferential arcuate race has an arc radius R of from 1.5 to 2.5millimeters.

The recessed circumferential arcuate race has a depth H from 0.05 to0.30 millimeters.

The number of ball-shaped grooves ranges from 20 to 80.

The ball-shaped grooves have a spherical radius r from 1.0 to 2.0millimeters.

The ball-shaped grooves have a depth h from 0.01 to 0.10 millimeters.

In the alternative self-tightening keyless chucks for gripping a toolshank, the upper bearing ring and the lower bearing ring may have thesame external dimensions and the same surface structure.

The upper bearing ring and the lower bearing ring may also havedifferent external dimensions and different surface structures, andtheir differences include the inside diameter and the thickness of thebearing rings.

During operation, the balls of the bearing assembly enter theball-shaped grooves of the bearing ring or the nut and are lockedtherein. Alternatively, the balls of the bearing assembly enter theball-shaped grooves of the upper bearing ring or the lower bearing ringand are locked therein. Thus, the nut is less susceptible to looseningin operation, so that the chuck maintains a great gripping force.

The present invention has an advantage that the depth of the ball-shapedgrooves which is essential to the anti-percussion ability of the chuckis determined by a mould.

That is, the optimum distance (i.e., depth of the ball-shaped grooves)between the ball-shaped grooves and the arcuate bottom surface of therecessed circumferential arcuate race has been determined during themanufacturing of the mould. In this way, the pressing of the members hasnothing to do with the adjustment or accuracy of the machine formanufacturing the members, whereby the depth of the ball-shaped groovesin all members can be constantly maintained within an optimum range toensure the anti-percussion performance of all chucks.

The present invention has another advantage that due to the use of therecessed arcuate race, the balls of the bearing assembly are constantlyconstrained within the arcuate race. This will ensure the centering ofthe members under force, so that the three jaws of the chuck aresubjected to a uniform force to thereby increase the gripping force.

The present invention has still another advantage that because the frontsleeve is press cast using a press-casting metal or a powderedmetallurgic material, the front sleeve has an increased strength and canbe directly engaged with the nut through press-fit to securely transmita torque.

By using the above configurations, the present invention overcomes theproblem that a conventional chuck either does not have a locking meansor has a locking means with unsatisfactory performance. The chuckaccording to the present invention can be operated in a quick, reliable,safe and convenient way. It provides such advantages as a reasonablestructure, a convenient assembly, a stable performance and a reliableoperation. The present invention can be used in all kinds of keyed orkeyless chucks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a self-tightening keyless chuck according tothe present invention.

FIG. 2 is an axial, longitudinal sectional view according to anembodiment of the present invention shown in FIG. 1.

FIG. 3A is a front view of a bearing ring according to an embodiment ofthe present invention.

FIG. 3B is a perspective view of a bearing ring according to anembodiment of the present invention.

FIG. 4A is a front view of a nut according to an embodiment of thepresent invention.

FIG. 4B is a perspective view of a nut according to an embodiment of thepresent invention.

FIG. 4C is a rear view of a nut according to an embodiment of thepresent invention.

FIG. 5 is a partially enlarged cross-sectional view of a ball-shapedgroove in an arcuate bottom surface of an arcuate race used in common bya bearing ring and a nut according to an embodiment of the presentinvention, i.e., an enlarged cross sectional view taken along line k-kin FIGS. 3A and 4A.

FIG. 6 is an axial, longitudinal sectional view according to anotherembodiment of the present invention shown in FIG. 1.

FIG. 7A is a partially enlarged view in which the balls of a bearingassembly are outside ball-shaped grooves (i.e., the balls are in anon-self-tightening state).

FIG. 7B is a partially enlarged view in which the balls of a bearingassembly are inside ball-shaped grooves (i.e., the balls are in aself-tightening state).

FIG. 8A is a front view of a nut according to another embodiment of thepresent invention.

FIG. 8B is a perspective view of a nut according to another embodimentof the present invention.

FIG. 8C is a rear view of a nut according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A detailed description of the present invention is provided withreference to the drawings and embodiments below.

FIG. 1 is a front view of a keyless chuck manufactured according to thepreferred embodiment of the present invention.

FIG. 2 is an axial, longitudinal sectional view of a self-tighteningchuck according to an embodiment of the present invention, wherein thechuck comprises a rear sleeve 1, a body 2, a bearing ring 3, a bearingassembly 4, a nut 5, a jaw 6, a front sleeve 7 and a stopper 8. Therelations of these elements are known in the art, and hence a detaileddescription thereof is omitted.

Referring to FIGS. 3, 4 and 5, the bearing ring 3 has a race surfacethat is provided with a circumferential arcuate race 9 with a fixeddepth. When viewed from the cross section along line k-k, thecircumferential arcuate race 9 has an arc radius R of 2.0 millimetersand a depth H of 0.15 millimeters. The circumferential arcuate race 9has an arcuate bottom surface that is provided with 40 ball-shapedgrooves 10, which have a spherical radius r of 1.5 millimeters and adepth h of 0.05 millimeters. Further, the surface of the nut 5 that actsas the other race of the bearing assembly 4 is also provided with ancircumferential arcuate race 9 and ball-shaped grooves 10 that areidentical in shape and number to those formed on the bearing ring 3.During operation, as shown in FIG. 7, the jaw grips a tool shank as thenut 5 rotates, and the balls of the bearing assembly 4 goes into/out ofthe ball-shaped grooves. FIG. 7A shows a non-self-tightening state ofthe balls of the bearing assembly 4 in which the balls are outside theball-shaped grooves. When the nut 5 is finally secured on the body 2,the balls of the bearing assembly 4 enter into the ball-shaped grooves10 in the upper or lower race and are locked therein. FIG. 7B shows aself-tightening state of the balls of the bearing assembly 4 in whichthe balls are in the ball-shaped grooves. Thus, the percussivevibrations transmitted through the body 2 of the chuck are unlikely toovercome the difference between the high and low energy states of theballs of the bearing assembly 4, the low energy state corresponding tothe location of the balls in the ball-shaped grooves. Depending upon thespecific application of the chuck and the expected impact loads duringoperation, the choice of having ball-shaped grooves in either or both ofthe race surfaces of the nut 5 and the bearing ring 3 and the number anddepth of the ball-shaped grooves can be optimized.

FIG. 6 is an axial, longitudinal sectional view of a self-tighteningchuck according to another embodiment of the present invention, whereinthe chuck comprises a rear sleeve 1, a body 2, an upper bearing ring 31,a bearing assembly 4, a lower bearing ring 32, a nut 5, a jaw 6, a frontsleeve 7 and a stopper 8. In this embodiment, the lower bearing ring 32is used as the other race of the balls of the bearing assembly 4 inplace of the nut 5 in the previous embodiment. The upper bearing ring 31and the lower bearing ring 32 may have the same external dimensions. Thesurface of at least one of the upper and lower bearing rings that facesthe bearing assembly 4 is provided with a recessed circumferentialarcuate race 9, and a plurality of ball-shape grooves 10 are uniformlyformed in an arcuate bottom surface of the arcuate race 9. The chuck inthis embodiment operates according to the same working principle as thatin the previous embodiment, and hence a detailed description thereof isomitted.

During assembly, the metal front sleeve 7 engages, through press-fit,with the nut 5 that is placed in a circular groove in the body 2 andsplit into two halves by split notches 11. Thanks to the strength andthe elastic/plastic deformability of the metal material per se, themetal front sleeve 7 is securely connected to the nut 5 throughpress-fit, thus ensuring transmission of an input torque. Beforepress-fit, the metal sleeve 7 is surface-treated by electrophoresispainting, static plastic spraying or anodized processing so that itssurface meets different requirements in color.

1. A self-tightening keyless chuck for gripping a tool shank,comprising: a rear sleeve (1); a body (2); a bearing ring (3); a bearingassembly (4); a nut (5); a jaw (6); a front sleeve (7); and a stopper(8), wherein the surface of at least one of the bearing ring (3) and thenut (5) that faces the bearing assembly (4) is provided with a recessedcircumferential arcuate race (9), and a plurality of ball-shape grooves(10) are uniformly formed in an arcuate bottom surface of the arcuaterace (9), and wherein the front sleeve (7) engages with the nut (5)through radial smooth press-fit.
 2. The self-tightening keyless chuckaccording to claim 1, wherein the nut (5) is provided with twoangularly-cut split notches (11) that are symmetrically positioned onboth ends of a diameter of the nut, the angularly-cut split notches (11)having a cut-out angle between 30 and 75°.
 3. A self-tightening keylesschuck for gripping a tool shank, comprising: a rear sleeve (1); a body(2); an upper bearing ring (31); a bearing assembly (4); a lower bearingring (32); a nut (5); a jaw (6); a front sleeve (7); and a stopper (8),wherein the surface of at least one of the upper bearing ring (31) andthe lower bearing ring (32) that faces the bearing assembly (4) isprovided with a recessed circumferential arcuate race (9), and aplurality of ball-shape grooves (10) are uniformly formed in an arcuatebottom surface of the arcuate race (9), and wherein the front sleeve (7)engages with the nut (5) through radial smooth press-fit.
 4. Theself-tightening keyless chuck according to claim 3, wherein the nut (5)is provided with two angularly-cut split notches (11) that aresymmetrically positioned on both ends of a diameter of the nut, theangularly-cut split notches (11) having a cut-out angle between 30 and75°, and wherein two parallel cut-out surfaces (13) are symmetricallyformed on the outer peripheral surface of the nut (5), which extenddownwards in an axial direction from the front end surface of the nut(5) by one third of the thickness of the nut and are located at an angleof 90° relative to the positions of angularly-cut split notches (11). 5.The self-tightening keyless chuck according to claim 1 or 3, wherein thefront sleeve (7) is press cast using a press-casting metal or a powderedmetallurgic material.
 6. The self-tightening keyless chuck according toclaim 1 or 3, wherein the recessed circumferential arcuate race (9) hasan arc radius R from 1.5 to 2.5 millimeters and a depth H from 0.05 to0.30 millimeters.
 7. The self-tightening keyless chuck according toclaim 1 or 3, wherein the number of ball-shaped grooves (10) ranges from20 to
 80. 8. The self-tightening keyless chuck according to claim 1 or3, wherein the ball-shaped grooves (10) have a spherical radius r from1.0 to 2.0 millimeters and a depth h from 0.01 to 0.10 millimeters. 9.The self-tightening keyless chuck according to claim 3, wherein theupper bearing ring (31) and the lower bearing ring (32) have the sameexternal dimensions and the same surface structure.
 10. Theself-tightening keyless chuck according to claim 3, wherein the upperbearing ring (31) and the lower bearing ring (32) have differentexternal dimensions and different surface structures, their differencesincluding the inside diameter and the thickness of the bearing rings.